1. Field of the Invention
This present invention relates generally to a dynamic image enhancement apparatus, and more particularly, to an apparatus for dynamically adjusting the saturation values of an image signal.
2. Description of the Prior Art
The natural way that human eyes perceive and respond to a color is based on hue, saturation and brightness. RGB color signals can be represented as two parts of luma (luminance or brightness) and chroma (the dominant color and its saturation). For processing image signals in a display device, luma-chroma separation is usually performed on the image signals first so as to enable us to adjust each component individually. When transmitting high-quality image signals, the brightness and color components are also separated and maintained individually, e.g. the YPbPr and YCbCr color spaces used in video and image compression. To enhance the saturation of image signals, one can adjust the Pb and Pr (Cb and Cr) components, i.e., the color component of the signal, to achieve this goal.
After displaying devices (e.g. monitors) are manufactured, users can make use of the OSD (On Screen Display) functionality built in the devices to change the default displaying settings, such as saturation, so as to further enhance the picture quality and obtain more vivid visual display. However, the same displaying settings usually are not suitable for all images. For example, raising the saturation of one image might cause another image originally with high saturation to be oversaturated, and vice versa. This scenario is often harmful to the visual effects presented by monitors.
By using the OSD controlling, users can easily configure the monitors to display images in their desired ways. However, the static settings cannot adapt to the dynamic changes occurred in a video sequence, causing the aforementioned problem. There is therefore a need for an apparatus that provides for automatic adjustment of saturation based on various image signals. Besides, there is also the possibility to accomplish the adjustment task in color spaces other than the widely used YPbPr and YCbCr, such as CIE Lab. The benefits of using CIE Lab include that the luma and chroma components of a color are well separated. Also, color data stored in CIE Lab representation can convert between different color spaces without loss of information.
Accordingly, an objective of the invention is to provide an apparatus for dynamically adjusting the saturation of an image signal.